Waste chromium production sludge from the Dubersay tailings dump is present in huge quantities with a magnesium oxide content of up to 40 %. The chrome-containing waste was sintered at 1 100 °C, the resulting sinter was mixed with sulphuric acid when heated to 300 °C. The resulting mixture after heating was leached with water at 90 °C, the solid precipitate was washed and dried to yield a chrome concentrate containing 55,4 % Cr2O3, 8,2 % SiO2. Evaporation of the purified solution produces magnesium sulphate which is a magnesium fertilizer.
